Acute peripheral arterial ischemia: a prospective evaluation of differential management with surgery or thrombolysis

In this three year prospective study of 177 patients with acute peripheral arterial ischemia those subjects with acute iliofemoral emboli or ischemia with a neurosensory deficit had urgent operations. The remainder included patients less likely to have limb salvage after surgery and who therefore were treated with thrombolytic therapy. This was done in three open studies of intravenous, acylated, plasminogen-streptokinase activator complex, low dose intraarterial streptokinase and intraarterial tissue-plasminogen activator (t-PA). The overall outcome after 30 days of thrombolytic therapy was limb salvage (55%), amputation (15%), and death (30%). The severity of the presenting ischemia was the most important prognostic indicator. In patients with a neurosensory deficit, limb salvage after either embolectomy or surgical reconstruction (59%) was more likely than after thrombolysis (31%). In patients without a neurosensory deficit, limb salvage after thrombolysis (68%) was better, though not significantly, than after surgery (53%). Local intraarterial thrombolysis with either streptokinase or t-PA produced an encouraging 66% limb salvage in 59 cases. In management of acute peripheral arterial occlusions an approach based on the severity of ischemia is optimal, with urgent surgery for patients with a neurosensory deficit and intraarterial thrombolytic therapy reserved as an alternative in selected cases with stable ischemia.

[The new thrombolytic agents]

Among the new thrombolytic agents, two are or will be available in the near future: plasminogen tissue activator and antistreplase or anysoiled plasminogen-streptokinase activator complex (APSAC). The repermeabilization rate provided by these two thrombolytic agents administered intravenously, is practically identical, close to 70 p. cent, i.e. comparable to that obtained by intracoronary administration of streptokinase. The rate of secondary reobstruction is estimated near 17 p. cent for the tissue plasminogen activator and 10 p. cent for APSAC. Secondary reobstruction would be more frequently observed with thrombolytics with a short half-life (5 to 8 minutes of the tissue plasminogen activator whether it has one or two chains, versus 90 minutes with APSAC). Other factors influence it: persistence of a thrombogenic stimulus at the site of the stenosis, presence of thrombin, platelet activation... Both products have been found to be effective in limiting the size of the myocardial infarction and preservation of the left ventricular function. Finally, both have been shown to be effective on the reduction of the immediate and long-term mortality during extensive multicentric trials. The tissue plasminogen activator, although specific for fibrin, results in haemorrhagic complications which are as frequent as those cause by anistreplase which does not present this specificity for fibrin. The fibrin of pathological thrombi and the fibrin of the haemostatic centrifugate are identical. It is therefore lysed in the same fashion by all thrombolytic agents, whether or not specific of fibrin.

[A european multicenter and randomized study of APSAC versus streptokinase in myocardial infarction]

In a multicentre randomized open study conducted on two parallel groups the effectiveness of APSAC was compared with that of streptokinase (SK) in 116 cases of myocardial infarction treated during the first 2.75 hours. APSAC (30 IU) was administered by intravenous bolus injection over 2 to 5 minutes, and SK (1.5 million IU) by intravenous infusion over 60 minutes. The patency of the coronary artery responsible for myocardial infarction was evaluated by coronary arteriography performed 1.74 h on average after the beginning of treatment; it was 70 p. 100 in the APSAC group and 51 p. 100 in the SK group (p less than 0.05). The fall in plasma fibrinogen was similar in both groups (mean minimum level; 0.2 g/l). Haemorrhages occurred in 9/58 patients treated with APSAC (15.5 p. 100) and in 13/58 patients treated with SK (22.4 p. 100); these haemorrhages took place during the first 24 hours in 4 patients of the APSAC group and in 10 patients of the SK group. Five patients died: 2 in the APSAC group and 3 in the SK group. In a subgroup of 38 patients who underwent 3 control coronary arteriographies (at 90 min, 24 hours and 3 weeks), the patency rates were 63 p. 100, 82 p. 100 and 93 p. 100 respectively with APSAC and 44 p. 100, 86 p. 100 and 92 p. 100 respectively with SK (NS). No coronary reocclusion occurred in the APSAC group, as against 3 (1 early, 2 delayed) in the SK group. It is concluded that APSAC seems to be more effective than intravenous streptokinase; it is easier to administer (bolus injection) and does not carry a higher risk of haemorrhage.

Reperfusion, patency and reocclusion with anistreplase (APSAC) in acute myocardial infarction

Because the reestablishment of coronary blood flow is believed to be central to the benefit of thrombolytic therapy, measurements of reperfusion (i.e., angiography before and after therapy), patency (i.e., angiography after therapy) and reocclusion rates are important to the evaluation of new thrombolytic therapies. For anisoylated plasminogen streptokinase activator complex (APSAC, anistreplase), comparisons have been made with control or placebo therapies to assess absolute efficacy, and with streptokinase to assess relative efficacy. In pooled experience from reperfusion studies, APSAC (30 U over 2 to 5 minutes) led to angiographic reperfusion in 55% of patients (98 of 177) who had symptoms of acute myocardial infarction (MI) for less than 6 hours. Among 107 patients treated with APSAC in angiographic patency studies, 69% (74) showed an open infarct-related artery 1 to 4 hours after therapy. (Patency rates are generally 10 to 20% greater than reperfusion rates, because some patients with acute MI may have a patent [subtotally occluded or spontaneously reperfused] infarct-related artery when entered into patency studies.) Using early peaking (less than or equal to 15 hours) of the creatine kinase curve as an indicator, a patency rate of 63% was observed among 387 patients treated with APSAC. The initial success rate with thrombolytic therapies is diminished by the rates of reocclusion and reinfarction, which must be accounted for in determining the net success of therapy. In 6 studies, a total of 87 patients with initially patent arteries after APSAC returned for reevaluation in 1 to 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased survival after APSAC: 30-day and 12-month mortality data from the APSAC Intervention Mortality Study

Preliminary analysis of mortality data from the anisoylated plasminogen streptokinase activator complex (APSAC) Intervention Mortality Study (AIMS) showed a 47% reduction in 30-day mortality (with a 95% confidence interval of 21 to 65%) for patients treated with APSAC within 6 hours of onset of acute myocardial infarction. After follow-up of 1,004 patients for 30 days after randomization in the double-blind, placebo-controlled, clinical trial, researchers found that 61 patients (12.2%) in the placebo group had died compared with 32 patients (6.4%) in the APSAC group (p = 0.0016). Incomplete follow-up of these patients for 1 year provided an estimated mortality of 19.4% in the placebo group and 10.8% in the APSAC group (log-rank test for survival to year p = 0.0006). Benefit was seen irrespective of age, site of infarction and time from onset of symptoms up to 6 hours.

Electrocardiographic evidence of myocardial salvage after thrombolysis in acute myocardial infarction

There is a need for a simple clinical measurement that will indicate the extent of myocardial salvage after successful thrombolysis. This study examined whether coronary artery reperfusion reduced the infarct size as assessed electrocardiographically after thrombolytic treatment. The sum of the (sigma) ST segment area in leads showing ST segment elevation in the 12 lead electrocardiogram at presentation was used as an index of potential myocardial injury (initial ischaemic index). The evolved infarct size at 48 h was assessed by a QRS scoring system. Two groups of patients, both admitted with anterior myocardial infarction within 6 h of onset, were studied. Group 1 (n = 35) received analgesia only and group 2 (n = 33) received thrombolytic treatment either by the intracoronary (streptokinase, n = 13) or intravenous route (anistreplase, n = 20). Reperfusion was assessed angiographically. The mean (SD) potential infarct size assessed by the initial ischaemic index was similar in both groups (group 1, sigma ST area = 115 (60) mm2 and group 2 = 126 (77 mm2). The QRS score representing evolved infarct size was significantly lower in the treated group (4.1 (2.5] than in group 1 (7.8 (2.6]. The 95% confidence intervals for QRS scores based on the admission sigma ST area from patients with successful reperfusion were applied to a third set of patients (n = 22) to test the ability of the admission ST area (myocardial injury) to predict the QRS score accurately. While patients with successful reperfusion had significantly lower QRS scores than those who did not (4.5 (3.1) versus 9.3 (3.4)), the wide confidence intervals caused by inter-individual variability precluded an accurate prediction of the QRS score in an individual from the sigma ST area at time of presentation. There was no difference in infarct size in patients treated early (</= 3 h) (QRS score 4.2(2.8)) or later (3-6 h) (4.1(2.1)). This study provides evidence that sequential electrocardiographic changes are reduced in patients with anterior infarction who achieve reperfusion after thrombolytic treatment and that this benefit is shown with treatment given up to six hours after infarct onset. None the less, the relation between the initial ischaemic index and the evolved QRS score has wide confidence intervals, reflecting inter-individual variability, and does not allow the prediction of a QRS score in an individual patient.

Relation of plasma D-dimer concentrations to coronary artery reperfusion before and after thrombolytic treatment in patients with acute myocardial infarction

This study was designed to investigate the possible role of pre- and posttreatment plasma D-dimer concentration as a reflection of coronary artery thrombolysis. Blood was collected from 206 patients with angiographically documented acute coronary occlusion presenting within 6 hours of symptom onset who were enrolled in a prospective study comparing intravenous APSAC (30 U) (IV-APSAC) with intracoronary streptokinase (160,000 U) (IC-SK). D-dimer concentrations in 104 patients after IV-APSAC therapy were higher than in 90 patients after IC-SK (mean +/- standard error, 1,009 +/- 60 vs 603 +/- 45, p less than 0.001), but there was no difference in patients with and without reperfusion (1,096 +/- 88 vs 875 +/- 67, p = 0.1 for IV-APSAC, and 587 +/- 48 vs 634 +/- 95, p = 0.6 for IC-SK). The median concentrations before treatment were similar in the IV-APSAC and IC-SK groups (93 and 90 ng/ml, respectively). These were higher than the value in 25 ambulatory control subjects (72 ng/ml) but lower than in 29 post-AMI (6 to 30 hours) patients and in preoperative orthopedic patients (140 ng/ml each). There was no difference in D-dimer concentrations in patients with grade 0 or grade 1 coronary artery occlusion (median 85 vs 90 ng/ml) or in patients with or without ultimate successful reperfusion (median 85 vs 93 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter trial of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) in acute myocardial infarction: effects on infarct size and left ventricular function

Two hundred thirty-one patients with a first acute myocardial infarction were randomly allocated within 5 h after the onset of symptoms either to treatment with anisoylated plasminogen streptokinase activator complex (APSAC), 30 U over 5 min, or to conventional heparin therapy, 5,000 IU in a bolus injection. Heparin was reintroduced in both groups 4 h after initial therapy at a dosage of 500 IU/kg per day. One hundred twelve patients received APSAC and 119 received heparin within a mean period of 188 +/- 62 min after the onset of symptoms. Both groups were similar in age, location of the acute myocardial infarction, Killip functional class and time of randomization. Elective coronary arteriography was performed on an average of 4 +/- 1.2 days after initial therapy. Follow-up radionuclide angiography and thallium-201 single photon emission computed tomography were performed before hospital discharge. Infarct size was estimated from single photon emission computed tomography and expressed as a percent of total myocardial volume. The patency rate of the infarct-related artery was 77% in the APSAC group and 36% in the heparin group (p less than 0.001). Left ventricular ejection fraction determined from contrast angiography was significantly higher in the APSAC group than in the heparin group. This was true for the entire study group (0.53 +/- 0.13 versus 0.47 +/- 0.12; p = 0.002) as well as for the subgroups of patients with anterior and inferior wall infarction (0.47 +/- 0.13 versus 0.40 +/- 0.11; p = 0.04 and 0.56 +/- 0.10 versus 0.51 +/- 0.11; p = 0.02, respectively). At 3 weeks, the difference remained significant for the anterior myocardial infarction subgroup. A significant 31% reduction in infarct size was found in the APSAC group (33% for the anterior infarction subgroup [p less than 0.05] and 16% for the inferior infarction subgroup [p = NS]). A close inverse relation was found between the values of left ventricular ejection fraction and infarct size (r = -0.73, p less than 0.01). By the end of a 3 week follow-up period, seven APSAC-treated patients and six heparin-treated patients had died. In conclusion, the early infusion of APSAC in acute myocardial infarction produced a high early patency rate, significant limitation of infarct size and significant preservation of left ventricular systolic function, mainly in anterior wall infarction.

[Socioeconomic implications of the practice of thrombolysis in the acute stage of myocardial infarction]

The use of variegated and costly thrombolytic agents for the treatment of myocardial infarction in its acute phase may have medico-social advantages. In the present study, these advantages were evaluated after one year from two age and sex matched populations: 40 patients who underwent thrombolysis and 38 patients who did not. Compared with the first hospitalizations, the difference was + 4,000 francs, rising to + 11.000 francs with the drug Eminase. A questionnaire including medical, social and economic data was sent to the 78 patients and was filled by 63 of them, remaining unanswered by one patient who had thrombolysis and 10 patients who did not. Readmission to hospital showed a 44.000 francs difference to the benefit of patients who underwent thrombolysis. Ancillary care and return to work were similar in both groups. Cost expectancy was 119.500 francs for patients who had thrombolysis and 122.000 francs for those who did not. Thrombolysis therefore is a cost reduction factor, but its influence on costs is less pronounced when it is performed soon after the onset of myocardial infarction. Thrombolysis is more expensive when carried out at home than in hospital. In this study, the excess cost (+ 5.000 francs) was due to the relatively small number of patients and to the loss of professional activity which may be an uncertain factor. Mortality at one year was nil when thrombolysis was performed within the first two hours (12 patients) and rose to 16.6 percent between 2 and 3 hours (18 patients) and 30 percent after 3 hours (10 patients). Conducted on a necessarily limited number of patients, this multiple criteria study was also aimed at establishing a method to evaluate the health expenditures imposed by the introduction of new and costly treatment in the management of myocardial infarction.

Pathogenesis and management of acute pulmonary embolism

Pulmonary embolism can produce severe cardiopulmonary dysfunction characterized by pulmonary artery hypertension, right ventricular failure, and hypoxemia. The search for the source of a pulmonary embolus, by exploration of the veins of the lower limbs and the inferior vena cava should be systematically carried out in all cases of pulmonary embolus which are not immediately life-threatening to the patient. The treatment of deep vein thrombosis associated with pulmonary embolism with thrombolytic agents has been proposed and utilized for approximately 20 years. Although superior results have been claimed with thrombolytic agents, the use of this type of treatment remains limited to massive or sub-massive pulmonary embolism. Fibrinolytic agents with high specificity for fibrin in the thrombi and little systemic activation of the fibrinolytic system have been developed and tested in preliminary clinical trials of patients with acute pulmonary embolism. The largest published experience available has been with recombinant tissue plasminogen activator (rtPA). The acylated streptokinase-plasminogen complex (APSAC) and pro-urokinase also gave promising results. All these agents were accompanied by unexpectedly high incidence of systemic activation of the fibrinolytic system and by hemorrhagic complications with frequencies similar to those that follows the use of first generation products (urokinase and streptokinase). Hence, their superior clinical efficacy must be clearly proven before they are substituted for a more widely available and less expensive drug, such as streptokinase.

Effect of reperfusion on electrocardiographic and enzymatic infarct size: results of a randomized multicenter study of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) versus intracoronary streptokinase in acute myocardial infarction

The effect of early coronary artery reperfusion on ECG and enzymatic parameters was examined in 240 patients with acute myocardial infarction. These patients had participated in a randomized trial comparing intravenous anisoylated plasminogen streptokinase activator complex (APSAC) (n = 123) and intracoronary streptokinase (n = 117) therapy. Reperfusion occurred in 59 of 115 (51%) patients receiving APSAC and 67 of 111 (60%) patients receiving streptokinase (p = NS). There was greater early resolution of ST segment elevation in the reperfused than in the nonreperfused patients (p less than or equal to 0.003) and more rapid Q wave evolution (p less than or equal to 0.03). Sigma Q was lower in reperfused than in nonreperfused patients at 8 hours (1.41 +/- 1.18 versus 2.11 +/- 2.10 mV; p less than or equal to 0.05) and at 24 hours (1.43 +/- 1.25 mV versus 2.08 +/- 1.88 mV; p less than or equal to 0.02). Time to peak level was shorter in the reperfused patients for creatine kinase (CK) (10.7 +/- 5.5 hours versus 14.9 +/- 5.9 hours; p less than 0.0001) and lactic acid dehydrogenase (LDH) (29.6 +/- 13.6 hours versus 34.4 +/- 10.5 hours; less than or equal to 0.03) enzymes. Peak LDH-1 was lower in the reperfused group (274 +/- 149 U/L versus 341 +/- 173 U/L; p less than or equal to 0.04). Reperfusion at a mean of 3.9 hours after the onset of infarction was associated with more rapid resolution of ST segment elevation, faster Q wave evolution, smaller ECG infarct size, earlier cardiac enzyme release, and smaller enzymatic infarct size than later or no reperfusion.

Value of myocardial defect size measured by thallium-201 SPECT: results of a multicenter trial comparing heparin and a new fibrinolytic agent

In a multicenter randomized double-blind trial comparing heparin and a new fibrinolytic agent, anisoylated plasminogen streptokinase activator complex (APSAC), 231 patients presenting with a less than 5 hr acute myocardial infarction underwent a contrast angiography (CA) before the end of the first week of admission, and radionuclide cardiac blood-pool imaging and a 201Tl single photon emission computed tomography (SPECT) study before the end of the third week. Left ventricular ejection fraction (LVEF) and a wall motion score (WM) were calculated from CA. LVEF was also obtained from cardiac blood-pool imaging, and defect size (DS) from 201Tl SPECT. Results demonstrated that all parameters were significantly improved in patients treated with APSAC versus heparin (contrast LVEF 53 +/- 13 vs. 47 +/- 14 p less than 0.01, WM 9.8 +/- 6.5 vs. 13.3 +/- 7.9 p less than 0.001, radionuclide LVEF 43 +/- 12 vs. 40 +/- 13 p less than 0.05, DS 14 +/- 12 vs. 18 +/- 14 p less than 0.05). When the patients were divided according to infarct site and infarct-related coronary artery patency, it was demonstrated with all four parameters that the beneficial effect of APSAC can be largely explained by the lower incidence of vessel obstruction in this group (37% vs. 77% in the heparin group, p less than 0.001). It is concluded that (a) when compared with heparin and in the conditions of the trial, APSAC significantly improves the cardiac function and decreases the DS and (b) DS measured by 201Tl SPECT is as valuable a quantitative parameter of therapeutic evaluation as are LVEF and WM.

The German multicenter trial of anisoylated plasminogen streptokinase activator complex versus heparin for acute myocardial infarction

A multicenter randomized trial of anisoylated plasminogen streptokinase activator complex (APSAC) versus heparin in patients with acute myocardial infarction of less than 4 hours' duration was undertaken in 19 hospitals. Of the 313 patients, 151 received heparin and 162 APSAC (30 U as intravenous injection). Within 28 days of hospital stay, 19 deaths (12.6%) occurred in the heparin group and 9 deaths (5.6%) in the APSAC group (p = 0.032). After 24 hours, patients in the APSAC group had a significantly lower incidence of cardiogenic shock (3.2 vs 9.5%, p = 0.031), asystole (3.8 vs 10.8%, p = 0.015) and need for resuscitation (5.1 vs 11.5%, p = 0.039). There was no difference in global and infarct-related ejection fraction between the 2 groups. Thus, APSAC favorably influences prognosis and clinical course in hospital.

Prehospital thrombolytic treatment of acute myocardial infarction with anisoylated plasminogen streptokinase activator complex

In cooperation with a group of general practitioners (GP), we investigated the possible risk and benefit of prehospital initiation of thrombolytic therapy in acute myocardial infarction (AMI) with anisoylated plasminogen streptokinase activator complex (APSAC) at the patient's home. During a 14-month period, 58 patients with suspected AMI were evaluated by their GP using a protocol with strict inclusion and exclusion criteria. The GP alerted a special mobile intervention team which administered APSAC at home in 13 of the 19 patients. Coronary reperfusion was achieved in ten of these 13 patients. Apart from short and easily treated episodes of bradycardia and/or hypotension after the injection of the thrombolytic drug in four of 13 patients, no major adverse events were noted in the early treatment period. The estimated time gain by treating the patient at home instead of starting the treatment in the coronary care unit was 46 +/- 14 min. Therefore, at-home initiation of thrombolytic treatment seems feasible, fast, and safe.

Thrombolytic treatment of pulmonary embolism with APSAC

BRL 26921 (Eminase registered trade mark in Belgium, Germany and The Netherlands) is the p-anisoyl derivative of the primary (human) lys plasminogen-streptokinase activator complex (APSAC). The acyl-enzyme has the theoretical advantage of causing fibrinolysis in situ in the presence of fibrin clotbound plasminogen. It was administered to 34 patients with severe pulmonary embolism (PE) in an open multicentre study. PE was suspected on clinical, blood gas, ECG, and radiographic data. Pulmonary angiograms performed pre- and post-treatment confirmed the diagnosis and were assessed using the Miller Index (MI). Fibrinogen, plasminogen, alpha-2-antiplasmin, fibrinogen degradation products (FDP), activated partial thromboplastin time (APTT), partial thromboplastin time (PTT) were closely monitored before and after each administration of APSAC. Median angiographic improvement was 50% (range 0-94%). The following adverse events were reported: bleeding at puncture sites (n = 12), haematuria (n = 1), epistaxis (n = 3), fever (n = 2). A blood transfusion was given in one patient with an inguinal haematoma. Systemic fibrinogenolysis occurred in 20/28 patients.

Comparison of intravenous anisoylated plasminogen streptokinase activator complex and intracoronary streptokinase in acute myocardial infarction

Coronary angiography was used to compare the efficacy of anisoylated plasminogen streptokinase activator complex (APSAC) administered intravenously and streptokinase given by intracoronary infusion in inducing reperfusion in patients with a proven acute myocardial infarction. Forty-two patients received 30 U of APSAC intravenously over 5 minutes and 43 patients received 250,000 IU of streptokinase given via intracoronary infusion over 90 minutes, after occlusion of the infarct-related vessel was demonstrated by angiography. Reperfusion was achieved in 23 (64%) of 36 patients (mean time to reperfusion 46 minutes) treated with APSAC and 25 (67%) of 37 patients (mean time to reperfusion 45 minutes) treated with intracoronary streptokinase, who were angiographically evaluated 90 minutes after the start of treatment. Twenty-four hours after treatment, reocclusion had occurred in 1 (5%) of 22 patients in the APSAC group and in 3 (13%) of 23 patients in the streptokinase group. No major bleeding was observed in either treatment group despite a similar systemic lytic state that lasted for up to 48 hours. Two patients treated with APSAC died after severe left ventricular failure unrelated to therapy. The results indicate that APSAC given intravenously is as effective as streptokinase given intracoronary in producing thrombolysis in acute myocardial infarction. The major advantages of APSAC are its rapid and convenient administration by a single intravenous injection, the low rate of arterial reocclusion and good patient tolerance.

Multicenter reperfusion trial of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) in acute myocardial infarction: controlled comparison with intracoronary streptokinase

The recent establishment of a firm therapeutic role for reperfusion in acute myocardial infarction has stimulated interest in the development of more ideal thrombolytic agents. Anisoylated plasminogen streptokinase activator complex (APSAC) is a new plasminogen activator possessing properties that are promising for intravenous thrombolytic application in acute myocardial infarction. To assess the reperfusion potential of intravenous APSAC, a multi-center, angiographically controlled reperfusion trial was performed. An approved thrombolytic regimen of intracoronary streptokinase served as a control. Consenting patients with clinical and electrocardiographic signs of acute myocardial infarction were studied angiographically and 240 qualifying patients with documented coronary occlusion (flow grade 0 or 1) were randomized to treatment in less than 6 h of symptom onset (mean 3.4 h, range 0.4 to 6.0) with either intravenous APSAC (30 U in 2 to 4 min) or intracoronary streptokinase (160,000 U over 60 min). Both groups also received heparin for greater than or equal to 24 h. Reperfusion was evaluated angiographically over 90 min and success was defined as advancement of grade 0 or 1 to grade 2 or 3 flow. Rates of reperfusion for the two treatment regimens were 51% (59 of 115) at 90 min after intravenous APSAC and 60% (67 of 111) after 60 min of intracoronary streptokinase (p less than or equal to 0.18). Reperfusion at any time within the 90 min was observed in 55 and 64%, respectively (p less than or equal to 0.16). Time to reperfusion occurred at 43 +/- 23 min after intravenous and 31 +/- 17 min after intracoronary therapy. The success of intravenous therapy was dependent on the time to treatment: 60% of APSAC patients treated within 4 h exhibited reperfusion compared with 33% of those treated after 4 h (p less than or equal to 0.01). Reperfusion rates were also dependent on initial flow grade (p less than or equal to 0.0001): 48% (81 of 168) for grade 0 (APSAC = 43%, streptokinase = 54%), but 78% for grade 1 (APSAC = 78%, streptokinase = 77%). APSAC given as a rapid injection was generally well tolerated, although the median change in blood pressure at 2 to 4 min was greater after APSAC than after streptokinase (-10 versus -5 mm Hg). Mean plasma fibrogen levels fell more at 90 min after the sixfold higher dose of APSAC than after streptokinase (to 32 versus 64% of control). Reported bleeding events were more frequent after APSAC but occurred primarily at the site of catheter insertion and no event was intracranial.(ABSTRACT TRUNCATED AT 400 WORDS)